1. Field
The present disclosure relates generally to commercial drying of produce; more specifically, it relates to removal of surface liquids from produce, including but not limited to leafy vegetables, using vertical or canted drum centrifugal driers.
2. Related Art
The commercial processing of fresh produce requires that once harvested, it be washed clean followed by sanitizing to provide a safe product with a useful shelf-life. In order to accomplish this cleaning and sanitizing, large volumes of water are used to provide mechanical cleaning while also being used to carry cleaners and sanitizers, like chlorine. While this results in a clean and sanitary product, the water added must be separated from the produce and either be sent to drain, recycled, or further processed for disposal.
Moisture that remains on the produce after packaging has a negative impact on shelf-life and product appeal. The amount of moisture can vary for many reasons including the product mix, piece sizes, time of year, and other factors. The removal of residual water from the surfaces of fresh, packaged produce is an important process for extending the shelf-life and maintaining the aesthetic appeal of the product after packaging. It is desired that the product be as dry as possible without causing dehydration of the leaves.
Drying can be accomplished in many ways: fluidized bed drying, spiral coolers, horizontal and vertical/canted drum drying, infrared, and many others. During processing, fresh vegetables are preferably maintained at or slightly below 4° C. This preference has commonly resulted in the use of centrifugal drum driers to both dewater and dry the product after washing and sanitation of the product. This preference has also led to less than successful or inconsistent removal of this surface water. During centrifugal drying, the produce is compacted by the weight of the produce on top of it and by the centrifugal force created by the dryer. This compaction of the produce and the resulting increased density of the produce are referred to as matting. Matting contributes to the problem of inconsistent drying and also causes bruising of the produce. As a spin cycle in a conventional centrifugal dryer nears completion, the produce is denser near the bottom and outer parts of the basket, and less dense near the top and inner parts of the basket. Since the produce becomes more difficult to dry as its density increases, the produce near the top of the basket is drier at the end of a spin cycle than the produce near the bottom of the basket. Inconsistent drying has an adverse impact on the quality of the product.
What is needed are processes and devices to dry produce thoroughly and consistently while minimizing drying cycle time and damage to the produce.